Metalworking fluid composition and method for its use in the machining of compacted graphite iron

ABSTRACT

Compositions and methods for reducing toolwear during iron-machining, including applying a composition comprising water; a lubricant ester; and a sulfur-containing lubricant additive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit from U.S. Provisional Patent Application No. 61/568,979, filed on Dec. 9, 2011, which is incorporated by reference in its entirety.

BACKGROUND

Cast irons may be used in the production of many industrial components. Certain types of cast irons such as compacted graphite iron may be difficult to machine; the metal cutting and grinding often necessary in the fabrication of industrial components may present challenges and difficulties resulting in, for example, rapid and accelerated rates of tool wear, as well as in reduced quality of the part produced.

With much effort currently underway in industry to replace standard gray cast irons with compacted graphite iron to produce lighter and higher strength parts, it is useful to describe the differences both structurally and compositionally which give rise to the differences in the material properties and machinability of these two metals. Gray cast iron has traditionally been used for the production of engine blocks, cylinder heads, as well as various other automotive components. The graphite in gray cast iron has a flake-like structure. The predominance of interconnecting graphite flakes gives rise to a high level of discontinuities and stress concentration effects in the matrix and subsequently gives rise to the properties characteristic of gray irons such as good thermal conductivity, damping capacity, and good machinability properties. Thus gray cast iron is easily machined at low production costs, (higher metal removal rates with long tool life). Different from gray cast iron, compacted graphite iron has a graphite structure much like that of coral. Such a graphite structure produces lower levels of discontinuities and stress concentration effects within the metal, giving rise to higher strength and toughness properties, as well as lower machinability.

In addition to graphite structure differences, there are significant compositional differences between gray cast iron and compacted graphite iron which also are largely responsible for the differences in the machinability of these two metals. The presence of sulfur in gray cast iron is considered to be a critical factor associated with the high machinability of this metal.

Due to these two factors (graphite morphology and sulfur concentration) the machinability of compacted graphite iron is considerably lower, and tool wear is considerably higher than that experienced in gray cast iron machining. Previously reported studies, show that tool life for milling and drilling operations of compacted graphite iron can be one half, while tool life in compacted graphite iron boring operations have been seen to be just one-tenth of that obtained in comparable machining operations with gray cast iron. Thus it has been clear that there has existed a need for technology advances enabling for improved and more economical machining of compacted graphite iron. Research and development in areas of tool engineering, optimization of machining conditions, compacted graphite iron composition, as well as metalworking fluid composition. The current invention describes new fluid compositions and methods of use which can provide enhanced tool life and part quality in the machining of common grades of compacted graphite iron.

SUMMARY OF THE INVENTION

According to some embodiments of the present invention, an iron-machining composition includes water; a lubricant ester; and a sulfur-containing lubricant additive. In some embodiments, a lubricant ester or combination of lubricant esters is present in an amount of about 1 wt % to about 50 wt %, and may include a polyol ester; a glycerol-based ester; and/or an ester selected from those of C₁₂ toC₁₈ fatty acid esters of 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, 2-hydroxy-1,3-propanediol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and 1,2,3-propanetriol. Suitable esters also may include those produced by the initial reaction of the polyol with ethylene oxide and/or propylene oxide followed by subsequent esterification, to yield a polyoxyalkylated polyol ester. Suitable esters also include those produced by the condensation of hydroxyl-functionalized fatty acids, such as ricinoleic acid, to yield oligomeric and polymeric esters.

In some embodiments, a sulfur-containing lubricant additive is present in an amount of about 0.1 wt % to about 20 wt % and may include sulfurized alpha olefins, di-branched alkyl tri and polysulfides, sulfur containing carboxylic acids, complex sulfurized esters, and/or a dialkyl polysufide selected from those having a formula: CH₃—C(R₁)(R₂)—(CH₂)n-)_(x)-S_(m), whereby R₁═H or CH₃, R₂═H or CH₃, n=8-20, x=1-2, and m=2-7.

In some embodiments, an iron-machining composition includes fatty acids such as those containing saturated and unsaturated chains of between 12 and 22 carbons, in an amount of about 0 wt % to about 12 wt %.

In some embodiments, an iron-machining composition includes about 0 wt % to about 10 wt % of a mixture of amine compounds having a formula R₁(R₂)—N—R₃, whereby R₁═H, CH₃ or —CH₂CH₂OH, R₂═H, CH3-(CH2)_(n), whereby n=0-22, —CH₂CH₂OH, or cyclic C₆H₁₁, and R₃═—(CH₂CH₂O)_(m)—H whereby m=1-12, CH3-(CH2)_(x)O— whereby x=0-8, or cyclic C₆H₁₁.

In some embodiments, an iron-machining composition includes about 0 wt % to about 30 wt % of a boric acid-amine adduct whereby the boric acid amine adduct may be comprised of a mixture of one or more structures including the amine salts of boric acid, boric acid-alkonaolamine esters including cyclic boroxine esters, and polyborate amine salts.

In some embodiments, an iron-machining composition includes about 0 wt % to about 50 wt % of a mineral oil. Suitable mineral oils may be pure or a mixture of mineral oils such as naphthenic and paraffinic oils of between about 15 cSt and about 30 cSt at 40 degrees centigrade.

In some embodiments, an iron-machining composition includes about 4 wt % to about 10 wt % of a mixture of nonionic and anionic emulsifiers.

According to some embodiments, a method of machining iron includes applying a fluid composition of the present invention (referred to as fluid concentrate) as a water dilution whereby prior to use in machining, the composition of the present invention is first diluted with water to give between 1% to 100% concentration of the fluid concentrate. In some embodiments, such application may reduce tool wear during machining of iron such as by about 5% to about 90% as compared to conventional lubricant fluids. In some embodiments, the machined iron is compacted graphite iron.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows axial forces measured during drilling;

FIG. 2 shows torque measured during drilling;

FIG. 3 illustrates tool wear after drilling;

FIG. 4 shows tool wear with various machining fluids;

FIG. 5 shows cutting forces with various machining fluids;

FIG. 6 shows tool wear obtained on drills; and

FIG. 7 shows the surface finish measured over one hundred thirty holes reamed.

DETAILED DESCRIPTION OF THE INVENTION

Compositions and methods of some embodiments of the present invention relate to metalworking fluid compositions and methods for their use in the machining of metal, such as iron. In some embodiments, compositions and methods of the present invention relate to machining compacted graphite iron (also referred to as “CGI” or “vermicular iron”). In some embodiments, fluid compositions and methods of application of the present invention which, when used in the metal cutting and grinding processes performed on iron such as compacted graphite iron, may significantly extend the lifetime of the tools used by effectively reducing wear, and may improve the quality of the part produced. In some embodiments, fluid compositions of the present invention include at least an ester lubricant in combination with a sulfur-containing lubricant additive.

Ester Lubricant

In some embodiments, fluid compositions of the present invention include one or more ester lubricants. Suitable ester lubricants may include polyol and natural carboxylic esters such as long chain (C₁₂-C₂₂) carboxylic esters of branched chained or cyclic mono, di and polybasic alcohols. Suitable ester lubricants may also include alkoxylated polyol esters such as long chain (C₁₂-C₂₂) carboxylic esters of branched chained or cyclic mono, di and polybasic alcohols whereby the polybasic alcohol is alkoxylated prior to formation of the carboxylic ester. Suitable esters may also include those produced by the condensation of hydroxyl-functionalized fatty acids, such as ricinoleic acid, to yield oligomeric and polymeric esters. In some embodiments, suitable ester lubricants include esters containing a carboxylic acid moiety selected from carboxylic acids with saturated and unsaturated alkyl chains of between 12 to 22 carbons in length, whereby fatty acid(s) are reacted with a mono or polyfunctional alcohol selected from but not limited to 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, 2-hydroxy-1,3-propanediol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and 1,2,3-propanetriol, to form the ester useful within the current invention.

In some embodiments, a fluid composition contains an ester lubricant in an amount of about 1 wt % to about 50 wt % of the fluid composition; about 2 wt % to about 40 wt % of the fluid composition; about 3 wt % to about 35 wt % of the fluid composition; about 4 wt % to about 30 wt % of the fluid composition; about 5 wt % to about 25 wt % of the fluid composition; about 6 wt % to about 20 wt % of the fluid composition; about 6 wt % to about 15 wt % of the fluid composition; about 7 wt % to about 10 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 4 wt % of the fluid composition; about 6 wt % of the fluid composition; about 8 wt % of the fluid composition; about 10 wt % of the fluid composition; about 12 wt % of the fluid composition; about 14 wt % of the fluid composition; about 16 wt % of the fluid composition; about 18 wt % of the fluid composition; about 20 wt % of the fluid composition; about 22 wt % of the fluid composition; about 24 wt % of the fluid composition; about 26 wt % of the fluid composition; about 28 wt % of the fluid composition; about 30 wt % of the fluid composition; about 32 wt % of the fluid composition; about 34 wt % of the fluid composition; about 36 wt % of the fluid composition; about 38 wt % of the fluid composition; about 40 wt % of the fluid composition; about 42 wt % of the fluid composition; about 44 wt % of the fluid composition; about 46 wt % of the fluid composition; about 48 wt % of the fluid composition; and about 50 wt % of the fluid composition.

Sulfur-Containing Lubricant Additives

In some embodiments, a fluid composition of the present invention includes one or more sulfur-containing lubricant additives. Suitable sulfur-containing additives may include sulfurized alpha olefins, di-branched alkyl tri and polysulfides, sulfur containing carboxylic acids, complex sulfurized esters, and/or dialkyl polysufides.

In some embodiments, suitable sulfur-containing compound include structures as shown in Formula 1:

CH₃—C(R₁)(R₂)—(CH₂)n-)_(x)-S_(m)   Formula 1:

-   -   whereby R₁═H or CH₃, R₂═H or CH₃, n=8-20, x=1-2, and m=2-7.

In some embodiments, a fluid composition include a sulfur-containing lubricant additive in an amount of about 0.1 wt % to about 20 wt % of the fluid composition; about 0.2 wt % to about 18 wt % of the fluid composition; about 0.3 wt % to about 16 wt % of the fluid composition; about 0.4 wt % to about 14 wt % of the fluid composition; about 0.5 wt % to about 12 wt % of the fluid composition; about 0.6 wt % to about 10 wt % of the fluid composition; about 0.7 wt % to about 10 wt % of the fluid composition; about 0.8 wt % to about 9 wt % of the fluid composition; about 0.9 wt % to about 8 wt % of the fluid composition; about 1 wt % to about 7 wt % of the fluid composition; about 7 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.2 wt % of the fluid composition; about 0.4 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 0.6 wt % of the fluid composition; about 0.8 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 3 wt % of the fluid composition; about 4 wt % of the fluid composition; about 5 wt % of the fluid composition; about 6 wt % of the fluid composition; about 7 wt % of the fluid composition; about 8 wt % of the fluid composition; about 9 wt % of the fluid composition; about 10 wt % of the fluid composition; about 12 wt % of the fluid composition; about 14 wt % of the fluid composition; about 16 wt % of the fluid composition; about 18 wt % of the fluid composition; or about 20 wt % of the fluid composition.

In addition to the above two components of the metalworking fluid, the composition of this invention may also contain other compounds commonly used in many metal cutting lubricant fluids. Such compounds and concentration of such compounds are described below.

Fatty Acids

In some embodiments, a fluid composition of the present invention includes fatty acids. Suitable fatty acids may include but are not limited to those of between 12 and 22 carbons in chain length incorporated into the formula as a single fatty acid type or as a combination of two or more fatty acids.

In some embodiments, a fluid composition of the present invention includes fatty acids in an amount of about 0 wt % to about 30 wt % of the fluid composition; about 0.1 wt % to about 30 wt % of the fluid composition; about 0.5 wt % to about 25 wt % of the fluid composition; about 1 wt % to about 20 wt % of the fluid composition; about 2 wt % to about 17 wt % of the fluid composition; about 3 wt % to about 15 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 3 wt % of the fluid composition; about 4 wt % of the fluid composition; about 5 wt % of the fluid composition; about 6 wt % of the fluid composition; about 7 wt % of the fluid composition; about 8 wt % of the fluid composition; about 9 wt % of the fluid composition; about 10 wt % of the fluid composition; about 11 wt % of the fluid composition; about 12 wt % of the fluid composition; about 13 wt % of the fluid composition; about 14 wt % of the fluid composition; about 15 wt % of the fluid composition; about 17 wt % of the fluid composition; about 20 wt % of the fluid composition; about 22 wt % of the fluid composition; about 25 wt % of the fluid composition; about 27 wt % of the fluid composition; or about 30 wt % of the fluid composition.

Amines

In some embodiments, a fluid composition of the present invention includes an amine or mixture of amine compounds. Suitable amines may include but are not limited to those having a formula R₁(R₂)—N—R₃, whereby R₁═H, CH₃ or —CH₂CH₂OH, R₂═H, CH3-(CH2)_(n), whereby n=0-22, —CH₂CH₂OH, or cyclic C₆H₁₁, and R₃═—(CH₂CH₂O)_(m)—H whereby m=1-12, CH₃—(CH₂)_(x)O— whereby x=0-8, or cyclic C₆H₁₁. Such amines include ethanolamine, triethanolamine, 2-amino-2-methyl propanol, dicyclohexylamine, and diglycolamine.

In certain embodiments, a fluid composition of the present invention includes an amine or mixture of amines in an amount of about 0 wt % to about 30 wt % of the fluid composition; about 0.1 wt % to about 30 wt % of the fluid composition; about 0.5 wt % to about 25 wt % of the fluid composition; about 1 wt % to about 20 wt % of the fluid composition; about 2 wt % to about 17 wt % of the fluid composition; about 3 wt % to about 15 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 3 wt % of the fluid composition; about 4 wt % of the fluid composition; about 5 wt % of the fluid composition; about 6 wt % of the fluid composition; about 7 wt % of the fluid composition; about 8 wt % of the fluid composition; about 9 wt % of the fluid composition; about 10 wt % of the fluid composition; about 11 wt % of the fluid composition; about 12 wt % of the fluid composition; about 13 wt % of the fluid composition; about 14 wt % of the fluid composition; about 15 wt % of the fluid composition; about 17 wt % of the fluid composition; about 20 wt % of the fluid composition; about 22 wt % of the fluid composition; about 25 wt % of the fluid composition; about 27 wt % of the fluid composition; or about 30 wt % of the fluid composition.

Amine-Boric Acid Adducts

In some embodiments, a fluid composition of the present invention includes a boric acid-amine adduct whereby the boric acid amine adduct may be comprised of a mixture of one or more structures which include the amine salts of boric acid, boric acid-alkonaolamine esters including cyclic boroxine esters, as well as polyborate amine salts. Suitable adducts can be prepared by the reaction of boric acid with a single or mixtures of amines selected from but not limited to monoethanolamine, triethanolamine, 2-amino-2-methyl propanol, dicyclohexylamine, and diglycolamine, reacted at either stoichiometric quantities or with slight excess of the amine component.

In certain embodiments, a fluid composition of the present invention includes an amine boric acid adduct in an amount of about 0.1 wt % to about 30 wt % of the fluid composition; about 1 wt % to about 25 wt % of the fluid composition; about 2 wt % to about 20 wt % of the fluid composition; about 3 wt % to about 17 wt % of the fluid composition; about 5 wt % to about 15 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 3 wt % of the fluid composition; about 4 wt % of the fluid composition; about 5 wt % of the fluid composition; about 6 wt % of the fluid composition; about 7 wt % of the fluid composition; about 8 wt % of the fluid composition; about 9 wt % of the fluid composition; about 10 wt % of the fluid composition; about 11 wt % of the fluid composition; about 12 wt % of the fluid composition; about 13 wt % of the fluid composition; about 14 wt % of the fluid composition; about 15 wt % of the fluid composition; about 17 wt % of the fluid composition; about 20 wt % of the fluid composition; about 22 wt % of the fluid composition; about 25 wt % of the fluid composition; about 27 wt % of the fluid composition; or about 30 wt % of the fluid composition.

Amine Salt of Dicarboxylic Acid

In some embodiments, a fluid composition of the present invention includes an amine salt of a short chain dicarboxylic acid. Suitable amine salts of short chain dicarboxylic acids include but are not limited to those whereby the amine diacid acid salt is comprised of a single or mixture of amines selected from monoethanolamine, triethanolamine, 2-amino-2-methyl propanol, dicyclohexylamine, and diglycolamine, reacted with a short chain dicarboxylic acid selected from those containing between 4-12 carbon atoms.

In certain embodiments of the present invention, a fluid composition includes one or more amine salts of a short chain dicarboxylic acid in an amount of about 0.1 wt % to about 20 wt % of the fluid composition; about 0.5 wt % to about 15 wt % of the fluid composition; about 1 wt % to about 10 wt % of the fluid composition; about 1.5 wt % to about 9 wt % of the fluid composition; about 2 wt % to about 8 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 1 wt % of the fluid composition; about 1.5 wt % of the fluid composition; about 2 wt % of the fluid composition; about 3 wt % of the fluid composition; about 4 wt % of the fluid composition; about 5 wt % of the fluid composition; about 6 wt % of the fluid composition; about 7 wt % of the fluid composition; about 8 wt % of the fluid composition; about 9 wt % of the fluid composition; about 10 wt % of the fluid composition; about 12 wt % of the fluid composition; about 14 wt % of the fluid composition; about 16 wt % of the fluid composition; about 18 wt % of the fluid composition; or about 20 wt % of the fluid composition.

Mineral Oil

In some embodiments, a fluid composition of the present invention includes a mineral oil. Suitable mineral oils may be pure or a mixture of mineral oils such as naphthenic and paraffinic oils. In some embodiments, a suitable mineral oil or mineral oil blend may have a final viscosity of about 5 cSt to about 35 cSt at 40 degrees centigrade; about 10 cSt to about 30 cSt at 40 degrees centrigrade; about 15 cSt to about 25 cSt at 40 degrees centrigrade; about 5 cSt at 40 degree centigrade; about 10 cSt at 40 degree centigrade; about 15 cSt at 40 degree centigrade; about 20 cSt at 40 degree centigrade; about 25 cSt at 40 degree centigrade; about 30 cSt at 40 degree centigrade; or about 35 cSt at 40 degree centigrade.

In certain embodiments, a fluid composition of the present invention includes a mineral oil or mineral oil blend in an amount of about 0 wt % to about 75 wt % of the fluid composition; about 0.1 wt % to about 75 wt % of the fluid composition; about 0.1 wt % to about 70 wt % of the fluid composition; about 0.1 wt % to about 65 wt % of the fluid composition; about 0.1 wt % to about 60 wt % of the fluid composition; about 0.1 wt % to about 55 wt % of the fluid composition; about 1 wt % to about 50 wt % of the fluid composition; about 2 wt % to about 45 wt % of the fluid composition; about 5 wt % to about 40 wt % of the fluid composition; about 10 wt % to about 35 wt % of the fluid composition; about 15 wt % to about 30 wt % of the fluid composition; about 20 wt % to about 25 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 5 wt % of the fluid composition; about 10 wt % of the fluid composition; about 15 wt % of the fluid composition; about 20 wt % of the fluid composition; about 25 wt % of the fluid composition; about 30 wt % of the fluid composition; about 35 wt % of the fluid composition; about 40 wt % of the fluid composition; about 45 wt % of the fluid composition; about 50 wt % of the fluid composition; about 55 wt % of the fluid composition; about 60 wt % of the fluid composition; about 65 wt % of the fluid composition; about 70 wt % of the fluid composition; or about 75 wt % of the fluid composition.

Emulsifiers

In some embodiments, a fluid composition of the present invention includes one or more emulsifiers. Suitable emulsifiers may include but are not limited to a mixture of nonionic and anionic emulsifiers selected from those commonly known in the art and typically used in water based metalworking fluids. In some embodiments, suitable emulsifiers include alkaline metal salts of alkylaryl, alkyl and aryl sulfonic acids; alkoxylated long chain alcohols of between C₁₂-C₂₂ in length; polyooxyethylene/polyoxypropylene copolymers; and ethoxylated alkyl phenols.

In some embodiments, a fluid composition of the present invention includes one or more emulsifiers in an amount of about 0.1 wt % to about 20 wt % of the fluid composition; about 0.5 wt % to about 18 wt % of the fluid composition; about 1 wt % to about 16 wt % of the fluid composition; about 2 wt % to about 14 wt % of the fluid composition; about 2 wt % to about 12 wt % of the fluid composition; about 3 wt % to about 11 wt % of the fluid composition; about 4 wt % to about 10 wt % of the fluid composition; about 0.1 wt % of the fluid composition; about 0.5 wt % of the fluid composition; about 1 wt % of the fluid composition; about 2 wt % of the fluid composition; about 3 wt % of the fluid composition; about 4 wt % of the fluid composition; about 5 wt % of the fluid composition; about 6 wt % of the fluid composition; about 7 wt % of the fluid composition; about 8 wt % of the fluid composition; about 9 wt % of the fluid composition; about 10 wt % of the fluid composition; about 11 wt % of the fluid composition; about 12 wt % of the fluid composition; about 13 wt % of the fluid composition; about 14 wt % of the fluid composition; about 15 wt % of the fluid composition; about 16 wt % of the fluid composition; about 17 wt % of the fluid composition; about 18 wt % of the fluid composition; about 19 wt % of the fluid composition; or about 20 wt % of the fluid composition.

Composition

A metalworking fluid composition described according to the present invention and suitable for use in the machining of iron such as compacted graphite iron consists of:

a) about 5 wt % to about 40 wt % of a lubricant ester or combination of lubricant esters selected from synthetic polyol fatty acid esters such as trimethyolpropane trioleate, pentaerythritol tetradodecanoate, neopentylglycol dioleate, and isopropyl oleate as well as those produced by the initial reaction of the polyol with ethylene oxide and/or propylene oxide followed by subsequent esterification, to yield a polyoxyalkylated polyol ester. As well as those produced by the condensation of hydroxyl-functionalized fatty acids, such as ricinoleic acid, to yield oligomeric and polymeric esters.

b) about 1 wt % to about 10 wt % of a sulfur-containing compound selected from di-branched alkyl polysulfides, sulfurized alpha olefins and complex sulfurized fatty acids and fatty acid esters;

c) about 0 wt % to about 12 wt % fatty acids selected from those of between 12 and 22 carbons in chain length which can be incorporated into the fluid as a single fatty acid or as a combination of two or more fatty acids;

d) about 3 wt % to about 15 wt % of an amine or mixture of amine compounds, selected from but not limited to those to those having a formula R₁(R₂)—N—R₃, whereby R₁═H, CH₃ or CH₂CH₂OH, R₂═H, CH3-(CH2)_(n), whereby n=0-22, —CH₂CH₂OH, or cyclic C₆H₁₁, and R₃═—(CH₂CH₂O)_(m)—H whereby m=1-12, CH₃—(CH₂)_(x)O— whereby x=0-8, or cyclic C₆H₁₁. Such amines include ethanolamine, triethanolamine, 2-amino-2-methyl propanol, dicyclohexylamine, and diglycolamine.

e) about 0 wt % to about 15 wt % of a boric acid-amine adduct whereby the boric acid amine adduct may be comprised of a mixture of one or more structures which include the amine salts of boric acid, boric acid-alkonaolamine esters including cyclic boroxine esters, as well as polyborate amine salts.

e) about 0 wt % to about 40 wt % of a paraffinic or naphthenic based mineral oil with an ambient temperature viscosity of between about 4 cSt to about 28 cSt.

Such fluid compositions, when blended in an amount of about 2 wt % to about 15 wt % in water, and utilized in the machining of iron such as compacted graphite iron, produce a significant decrease in the rate of tool wear which occurs as well as a noticeable enhancement in the quality of the part machined.

In another embodiment of the current invention, a fluid useful for the improved machining of iron such as compacted graphite iron includes:

a) about 5 wt % to about 15 wt % of a lubricant ester or combination of lubricant esters selected from those of C₁₈ fatty acid esters of 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, 2-hydroxy-1,3-propanediol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and 1,2,3-propanetriol;

b) about 2 wt % to about 5 wt % of a dialkyl polysufide selected from those according to Formula 1 whereby R₁═CH₃, R₂═CH₃, n=8-10 and m=3-5;

c) about 6 wt % to about 12 wt % fatty acids selected from those containing saturated and unsaturated chains of between 16 and 22 carbons;

d) about 3 wt % to about 10 wt % of a mixture of amine compounds, such as those described by Formula 2:

R₁(R₂)—N—R   Formula 2:

whereby R₁═H or —CH₂CH₂OH, R₂═H, or —CH₂CH₂OH, or cyclic C₆H₁₁, and R₃═ or —CH₂CH₂OH, or cyclic C₆H₁₁;

e) about 10 wt % to about 14 wt % of an amine-boric acid adduct according to the structure shown in Formula 3:

B(O⁻ HN⁺(CH₂CH₂OH)_(n))_(m)   Formula 3:

whereby n=m=3;

f) about 30 wt % to about 40 wt % of a naphthenic-based mineral oil with an ambient pressure viscosity of between about 15 cSt and about 30 cSt at 40 degrees centigrade; and

g) about 4 wt % to about 10 wt % of a mixture of nonionic and anionic emulsifiers selected from those commonly known in the art and typically used in water based metalworking fluids.

Such fluid compositions, when blended in an amount of about 3 wt % to about 15% in water, and utilized in the machining of iron such as compacted graphite iron, produce a noticeable decrease in the rate of tool wear which occurs as well as a noticeable enhancement in the quality of the part machined. Results of machining tests described below show the utility and advancement realized with such compositions in the machining of iron such as compacted graphite iron.

In some embodiments, fluid compositions of the present invention may be blended with water to prepare a dilution. In some embodiments, fluid compositions of the present invention may be blended in water in an amount of about 1 wt % to about 50 wt % of the dilution; about 2 wt % to about 25 wt % of the dilution; about 3 wt % to about 20 wt % of the dilution; about 3 wt % to about 17 wt % of the dilution; about 4 wt % to about 15 wt % of the dilution; about 1 wt % of the dilution; about 2 wt % of the dilution; about 3 wt % of the dilution; about 4 wt % of the dilution; about 5 wt % of the dilution; about 6 wt % of the dilution; about 7 wt % of the dilution; about 8 wt % of the dilution; about 9 wt % of the dilution; about 10 wt % of the dilution; about 11 wt % of the dilution; about 12 wt % of the dilution; about 13 wt % of the dilution; about 14 wt % of the dilution; about 15 wt % of the dilution; about 17 wt % of the dilution; about 20 wt % of the dilution; about 25 wt % of the dilution; or about 30 wt % of the dilution.

In some embodiments, use of fluid compositions according to embodiments of the present invention during machining iron such as compacted graphite iron results in a reduction in tool wear as compared to conventional fluids of about 5% to about 95%; about 10% to about 90%; about 15% to about 85%; about 20% to about 80%; about 25% to about 75%; about 30% to about 70%; about 35% to about 65%; about 40% to about 60%; about 5%; about 10%; about 15%; about 20%; about 25%; about 30%; about 35%; about 40%; about 45%; about 50%; about 55%; about 60%; about 65%; about 70%; about 75%; about 80%; about 85%; about 90%; or about 95%.

EXAMPLES

To assess the performance of a preferred composition as described according to the present invention, drilling of Grade 450 compacted graphite iron was performed. Drilling is a process whereby holes are produced in the workpiece metal, and in such, greater amounts of metal are removed, which typically requires greater cutting forces and gives rise to more severe mechanical and thermal conditions in the process. Assessment of fluid performance is made by measurement of the cutting forces and tool wear occurring during the drilling operation.

Example 1

In this example, a standard conventional ferrous machining fluid was assessed relative to a fluid described according to embodiments of the current invention.

Fluid A, useful for the improved machining of compacted graphite iron, was prepared according to embodiments of the present invention having:

a) about 5 wt % to about 10 wt % ester lubricant;

b) about 3 wt % to about 7 wt % of a sulfur additive;

c) 8 wt % to about 16 wt % mineral oil; and

d) the balance having amines, boric acid, fatty acids, and emulsifiers.

Fluid A was tested at a concentration of 8%. The machining conditions are as follows:

CGI Drilling Workpiece Grade 450 CGI Tool Gehring # 5514 0.25″ dia. Firex coated solid carbide Speed 3000 RPM (196 SFM) Feed 10.4 IPM (.00346 ipr) Depth 1.25″ through hole Fluid 8% in 130 ppm water Measured Parameters Cutting Forces Tool Wear CGI Drilling

The axial machining forces and torque (tangential forces) measured during drilling provide a useful indication of the friction in the cutting zone and the lubrication provided by the metalworking fluid. The change in the forces measured as drilling continues may provide a useful indirect measure of the change or deterioration in the condition of the tool, typically arising from tool wear and/or metal adhesion on the cutting edge. As seen in the results obtained and plotted in FIGS. 1 and 2, use of Fluid A (embodiment of current invention) enables for the machining of compacted graphite iron at considerably lower cutting forces and change in forces relative to that which occurs when the conventional ferrous machining fluid (Fluid B) is used.

In assessing the impact on the tool wear which occurs, it can be seen that the flank wear formed on the drill used during machining with the conventional ferrous machining fluid (Fluid B) resulted in about 69.2% greater wear on the flank face of the tool's cutting edge, relative to that obtained when using the fluid composition described in the current invention (Fluid A). Thus from both the cutting forces measured and the tool wear measured, the benefit and utility offered by the composition described in the current invention, is clearly seen in the drilling operation conducted.

Example 2

Fluid D, useful for the improved machining of compacted graphite iron, was prepared according to embodiments of the present invention having:

a) about 22 wt % to about 28 wt % of a lubricant ester selected from either the C₁₈ fatty acid ester of 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, or 1,2,3-propanetriol;

b) about 2 wt % to about 5 wt % of a dialkyl polysufide selected from those according to Formula 1 whereby R₁═CH₃, R₂═CH₃, n=8-10 and m=3-5;

c) about 3 wt % to about 6 wt % fatty acids comprised of those which include saturated alkyl chains of between 10 to 16 carbons along with longer chain length carboxylic acids comprised of saturated and unsaturated alkyl chains of between 18 to 22 carbon atoms in length.

d) about 3 wt % to about 8 wt % of a mixture of amine compounds, consisting of those described by Formula 2, whereby R₁═H or —CH₃, R₂═—CH₂CH₂OH, or cyclic C₆H₁₁, and R₃═—CH₂CH₂OH, or cyclic C₆H₁₁;

e) about 35 wt % to about 45 wt % of a naphthenic-based mineral oil with an ambient pressure viscosity of between about 15 cSt to about 30 cSt at 40 degrees centigrade; and

f) about 4 wt % to about 10 wt % of a mixture of nonionic and anionic emulsifiers selected from those commonly known in the art and typically used in water-based metalworking fluids.

Such fluid compositions, when in an amount of about 4 wt % to 15 wt % in water, and utilized in the machining of iron such as compacted graphite iron, produce a noticeable decrease in the rate of tool wear which occurs as well as a noticeable enhancement in the quality of the part machined. Fluid D was tested in drilling tests along with two currently used compacted graphite iron machining fluids which are based on conventional ferrous machining fluid compositions. These two fluids designated Fluid C and Fluid E, both represent the state of the art technology available for compacted graphite iron machining prior to that of the current fluid compositions described in this invention. Also included in this testing and comparison is Fluid A.

The results of tool wear measured during compacted graphite iron drilling using the four fluids is shown below in FIGS. 3 and 4. The results demonstrate that Fluid A and Fluid D clearly yield a significant reduction in tool wear, and thus extend the useful duration of the tooling. The results show that Fluid A and Fluid D result in a range of tool wear reduction between about 22% to about 46% representing significant benefit with regard to the machining operations and the cost associated with the process.

Example 3

Fluid F, useful for the improved machining of compacted graphite iron, was prepared according to embodiments of the present invention having:

a) about 12 wt % to about 18 wt % of a lubricant ester or combination of lubricant esters selected from those of C₁₈ fatty acid esters of 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, 2-hydroxy-1,3-propanediol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and 1,2,3-propanetriol. b) between 2 and 5% of a dialkyl polysufide selected from those according to Formula 1 whereby R₁═CH₃, R₂═CH₃, n=8-10 and m=5-8;

c) about 1 wt % to about 7 wt % fatty acids selected from those containing saturated and unsaturated chains of between 16 and 22 carbons;

d) about 8 wt % to about 14 wt % of a mixture of amine compounds, consisting of those described by Formula 2 whereby R₁═H or —CH₂CH₂OH, R₂═H, or —CH₂CH₂OH, and R₃═—CH₂CH₂OH, or —C₃H₆OH;

e) about 5 wt % to about 9 wt % of an amine salt of boric acid according to the structure shown in Formula 3:

B(O⁻ HN⁺(CH₂CH₂OH)_(n))_(m)   Formula 3:

whereby n=m=3;

f) about 40 wt % to about 55 wt % of a naphthenic-based mineral oil with an ambient pressure viscosity of between 15-30 cSt at 40 degrees centigrade; and

g) about 4 wt % to about 15 wt % of a mixture of nonionic and anionic emulsifiers selected from those commonly known in the art and typically used in water based metalworking fluids.

Such fluid compositions, when blended in an amount of about 4 wt % to about 15 wt % in water, and utilized in the machining of iron such as compacted graphite iron, produce a noticeable decrease in the rate of tool wear which occurs as well as a noticeable enhancement in the quality of the part machined.

Fluid F was tested in the drilling and reaming of Grade 450 CGI at a concentration of 8%. This fluid composition was tested along with and compared to the performance of a conventional machining fluid utilized for cast iron machining (including CGI), Fluid G. Fluid G is similar to Fluid F in composition but does not contain the sulfur based additive.

Along with CGI, these two fluids were also tested in the drilling and reaming of a common Class 40 gray cast iron. This testing was performed not only to demonstrate the utility of the fluid compositions described in this invention, but also the inherent difficulty associated with the machining of CGI relative to gray cast iron.

The torque (tangential forces) measured during drilling provides a useful indication of the friction in the cutting zone and the lubrication provided by the metalworking fluid. The change in the torque measured as drilling continues reflects the changes (wear) occurring on the tools cutting edge as drilling continues. In examining the results shown in FIG. 5, the lower machinability and greater challenge inherent in the machining of compacted graphite iron relative to a standard Class 40 gray cast iron is clearly seen.

The results also demonstrate that the use of a fluid according to embodiments of the present invention (Fluid F) provides significant enhancement in the machining process with much reduced cutting forces. This effectiveness of the preferred composition is also seen in the tool wear measured following drilling. FIG. 6 shows the tool wear obtained on the drills used. As seen and consistent with the cutting forces measured, while significantly higher wear occurs in compacted graphite iron machining relative to gray cast iron machining, the use of Fluid F enables for the effective reduction of wear on the tool cutting edge.

Although a reaming operation, which is performed at lower cutting speeds with less metal removal is considered to be a less severe operation to that of drilling, there may still be significant performance improvement obtained through use of a fluid composition according to embodiments of the present invention. Following drilling, the holes were reamed using a six fluted solid carbide reamer. The surface finish measured over the one hundred thirty holes reamed are shown in FIG. 7. It is seen that with use of the conventional ferrous machining fluid (Fluid G) rougher reamed hole surfaces are obtained very quickly, the use of Fluid F yields a significant improvement in the reamed hole surface roughness obtained.

Example 4

Boring of engine cylinders is one of the more critical operations in engine production, requiring high quality surfaces to be produced at relatively high cutting speeds. It is at such elevated cutting speeds (250-700 m/min), consistent with those used in many current high speed transfer lines, where the machinability differences between compacted graphite iron and conventional gray cast irons may be most pronounced. Previous studies have reported insert wear rates to be 20-30 times greater in the continuous cutting of compacted graphite iron relative to that obtained in the machining of gray cast iron under equivalent conditions.

In this example, a standard conventional ferrous machining fluid (Fluid B) along with a fluid described according to embodiments of the current invention were assessed in a turning operation utilized to simulate the continuous cutting conditions which occur during engine cylinder boring. Fluid A, useful for the improved machining of compacted graphite iron, was prepared according to embodiments of the present invention having:

a) about 5 wt % to about 10 wt % ester lubricant;

b) about 3 wt % to about 7 wt % of a sulfur additive;

c) 8 wt % to about 16 wt % mineral oil; and

d) the balance having amines, boric acid, fatty acids, and emulsifiers.

Fluid A was tested at a concentration of 9%. The machining conditions are as follows:

-   -   Carbide Grade KC-9120 cutting insert with 5° radial and 5° axial         angle     -   Speed=250 m/min, f=0.3 mm-rev, Ap=0.2 mm

Measured Parameter—Insert Wear

In assessing the impact on the tool wear which occurs, using the conventional ferrous machining fluid (Fluid B), machining continued for 10.75 Km of cutting distance before severe wear and failure of the tool was reached. Using the fluid composition described in the current invention (Fluid A), using identical machining conditions, machining continued for 14 Km of cutting distance before insert failure was reached. Thus under the high speed cutting conditions a 30% reduction in insert wear was obtained using the fluid described in the current invention. 

What is claimed is:
 1. An iron-machining composition comprising (a) water; (b) a sulfur-containing lubricant additive; and (c) optionally containing a lubricant ester in an amount of about 0 wt % to about 50 wt % of the iron-machining composition.
 2. The composition of claim 1, wherein the lubricant ester comprises about 0.05 wt % to about 50 wt % of the iron-machining composition.
 3. The composition of claim 1, wherein the lubricant ester comprises a polyol ester selected from those of C₁₂ toC₁₈ fatty acid esters of 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, 2-hydroxy-1,3-propanediol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and 1,2,3-propanetriol.
 4. The composition of claim 1, wherein the lubricant ester comprises a glycerol-based ester.
 5. The composition of claim 4, wherein the lubricant ester comprises a glycerol ester of C₁₂ to C₁₈ saturated and unsaturated fatty acids.
 6. The composition of claim 5, wherein the ester is derived from vegetable oils and animal fats.
 7. The composition of claim 5, wherein the ester is synthetically produced via the reaction of fatty acids with glycerol.
 8. The composition of claim 1, wherein the lubricant ester comprises a polyol ester produced by the initial reaction of the polyol with ethylene oxide and/or propylene oxide followed by subsequent esterification, to yield a polyoxyalkylated polyol ester.
 9. The composition of claim 1, wherein the lubricant ester comprises a oligomeric or polymeric ester produced by the condensation of hydroxyl-functionalized fatty acids, such as ricinoleic acid.
 10. The composition of claim 1, wherein the lubricant ester comprises C₁₈ fatty acid esters of 2,2 dimethyl-1,3-propanediol, 2-propanol, 1,1,1, tris(hydroxymethyl)propane, 2-hydroxy-1,3-propanediol, 2,2-bis(hydroxymethyl)-1,3-propanedioI, 1,2,3-propanetriol, or combinations thereof.
 11. The composition of claim 1, wherein the lubricant ester is present in an amount of less than about 50 wt % of the iron-machining composition.
 12. The composition of claim 1 wherein the sulfur-containing lubricant additive is selected from the group consisting of sulfurized alpha olefins, di-branched alkyl tri and polysulfides, sulfur containing carboxylic acids, complex sulfurized esters, and/or dialkyl polysufides.
 13. The composition of claim 1, wherein the sulfur-containing lubricant additive comprises a dialkyl polysufide selected from those having a formula: CH₃—C(R₁)(R₂)—(CH₂)n-)_(x)-S_(m) whereby R₁═H or CH₃, R₂═H or CH₃, n=8-20, x=1-2, and m=2-7.
 14. The composition of claim 1, wherein the sulfur-containing lubricant additive is present in an amount of about 0.5 wt % to about 7 wt %.
 15. The composition of claim 1, further comprising fatty acids selected from those containing saturated and unsaturated chains of between 12 and 22 carbons, in an amount of about 0 wt % to about 12 wt %.
 16. The composition of claim 1, further comprising about 3 wt % to about 15 wt % of a mixture of amine compounds having a formula R₁(R₂)—N—R, whereby R₁═H, CH₃ or —CH₂CH₂OH, R₂═H, CH3-(CH2)_(n), whereby n=0-22, —CH₂CH₂OH, or cyclic C₆H₁₁, and R₃═—(CH₂CH₂O)_(m)—H whereby m=1-12, CH₃—(CH₂)_(x)O— whereby x=0-8, or cyclic C₆H₁₁.
 17. The composition of claim 16, wherein the amine comprises ethanolamine, triethanolamine, 2-amino-2-methyl propanol, dicyclohexylamine, diglycolamine, or combinations thereof.
 18. The composition of claim 1, further comprising about 0 wt % to about 15 wt % of an amine-boric acid comprising alkanolamine borate esters, amine polyborate, amine salts of boric acid, and combinations thereof.
 19. The composition of claim 1, further comprising about 0 wt % to about 40 wt % of a mineral oil, the mineral oil comprising a paraffinic oil, naphthenic oil, or mixtures thereof, with an ambient pressure viscosity of between about 15 cSt and about 30 cSt at 40 degrees centigrade.
 20. The composition of claim 1, further comprising about 4 wt % to about 10 wt % of a mixture of nonionic and anionic emulsifiers.
 21. A method of machining iron, comprising applying the fluid composition of claim 1 to the iron during machining.
 22. A method of machining iron, comprising applying the fluid composition of claim 1 in the form of a water dilution, to the iron during machining.
 23. A method according to claim 22, whereby the fluid composition of claim 1 is diluted in water to a concentration of between 2% by wt. to 50% by weight prior to use in machining of iron.
 24. A method according to claim 22, whereby the fluid composition of claim 1 is diluted in water to a concentration of between 2% by wt. to 15% by weight prior to use in machining of iron
 25. A method of reducing tool wear during machining of iron, comprising applying the fluid composition of claim 1 at to the iron during machining.
 26. A method of claim 25 wherein reduced tool wear during machining of iron is achieved by use of the fluid composition diluted in water to a concentration of between 2% by wt to 50% by wt.
 27. A method of claim 25 wherein reduced tool wear during machining of iron, is achieved by use of the fluid composition diluted in water to a concentration of between 2% by wt to 15% by wt.
 28. The method of claim 25, wherein the tool wear is reduced by about 5% to about 90% as compared to conventional lubricant fluids.
 29. The method of claim 21, wherein the iron comprises compacted graphite iron. 